The present invention relates to a method for producing printed products in a production plant, equipped with a digital printing press and at least one post-print processing machine that is arranged downstream of the digital printing press. The printed products are produced in accordance with work orders, which are processed in that the digital printing press prints images and process-technical elements onto a print material web, transported with a first web speed in a conveying direction. The at least one post-print processing machine further produces printed products from the print material web, wherein the production plant is changed over if different printed products are to be produced during a following work order, as compared to a previous work order. The conversion involves adjusting at least one of the post-print processing machines during a conversion interval, wherein the web material is transported further by the digital printing press during the conversion interval.
As compared to traditional printing presses, digital printing presses offer ideal preconditions for printing small editions of printed products such as books, magazines, newspapers and the like. Processes such as the manufacturing of printing plates, the use of print rollers and the set-up costs are omitted completely since the book data can be used directly for the printing process with the digital printing process. In order for these advantages to be used in a production plant, consisting of a digital printing press and at least one post-print processing machine, new and innovative solutions are required during the post-print processing.
A digital printing press can generally print on an endlessly circulating paper web having a width of approximately 1 m, at a rate of up to about 4 m/s. In the process, technical elements such as print and/or cutting marks, barcodes for identifying individual pages and the like are also printed on the paper web in addition to the printed images. The paper web is imprinted sequentially, meaning during a single run and in the correct sequence in which the pages are supposed to be arranged in the future product, following all post-print processing operations.
As a result of this sequential printing, small editions can be produced immediately following each other. With a single-copy edition of a printed product, products having differing contents are printed successively. If other parameters of the printed product also change, e.g. format, thickness, height, width of the printed product, the downstream arranged post-print processing machines must also be adjusted accordingly.
Adjusting an individual post-print processing machine of this type, embodied as thread stitcher, is known from the European patent document EP 2492107 A1. For this, a predetermined sequence for a clocked processing of printed products is input into a central control unit, and the sequence is then processed in the control unit. If it is determined that the time available for adjusting the post-print processing machine is not sufficient, at least one idle cycle is inserted. With an idle or empty cycle of this type, no printed product is conveyed further and a gap develops in the material flow of the post-print processing machine during the adjustment phase, which is then detected in a downstream-arranged additional machine, e.g. a sewing station, and is transformed to a dummy pass. To be sure, this thread-stitching machine can process printed products of various formats within a uniform production operation, but the necessary adjustment of the post-print processing machine is possible only during an interval which corresponds to a multiple of an idle cycle. Accordingly, the time for this adjustment is not infinitely variable.
An arrangement for producing individual books or very small editions is described in German patent document DE 102008033184 A1, for which a post-print processing machine embodied as an adhesive binder is connected to at least one digital printing press to form a production plant or plant. If the production plant must be converted because of different formats and features for the books to be processed, then the adhesive binder, for example, is correspondingly adjusted by respectively inserting at least one idle cycle. Waste paper is produced during this adjustment period, wherein each idle cycle causes a time loss in the production process.